1. Field of the Invention
The present invention relates to a method of producing or machining a honeycomb structure molding die such as an extrusion die which is designed to form a honeycomb structure body of ceramic material employed as a catalyst carrier of an exhaust gas purifying filter for motor vehicles.
2. Description of the Related Art
For example, a honeycomb structure body is applicable to an exhaust gas purifying filter for motor vehicles. The honeycomb structure body is produced by extrusion molding using a honeycomb structure body molding die (hereinafter, will also be referred to as the “molding die” for short).
In general, such a molding die has a plurality of feed holes and a plurality of slit grooves (as thin grooves or slots). The slit grooves are formed in a lattice arrangement and communicate with the feed holes. Molding material such as ceramic material is supplied through the fed holes of the molding die. The molding material is then shaped in a honeycomb structure body by extrusion molding through a plurality of slit grooves of the molding die.
There are related art documents disclosing a method of producing such a honeycomb structure molding die to be used in extrusion molding, for example, Japanese patent No. 3750348 and Japanese patent No. 3814849.
In the related art method of producing or machining a molding die, metal material such as a die material is firstly prepared. A plurality of feed holes is then formed in the metal material from one end surface with a predetermined depth so as to not reach the other surface of the metal material, namely, not pass through the metal material. Following, a plurality of slit grooves is made in a lattice arrangement in the other surface side by cutting the other surface of the metal material using a thin circular grindstone blade as a cutting tool. The slit grooves are thereby communicated with the feed holes in the molding die.
However, such a related art method of producing or machining the honeycomb structure molding die involves the possibility of generating and attaching fine metal powder produced by cutting the metal material (die material) using the thin circular grindstone blade as the cutting tool. As a result, the slit grooves are thereby formed in a zigzag direction, not formed in a straight-line direction or a line direction approximating a straight line, in the molding die. Further, the related art method involves the possibility of generating thermal energy by friction between fine metal powder (generated by cutting the metal material) attached to the thin circular grindstone blade and the metal material as the die material to be worked, and the possibility of the thin circular grindstone blade seizing. As a result, the thin circular grindstone blade is broken and slit grooves of a wide width, wider than a desired width, are made in the molding die. It is therefore difficult for the related art methods to produce the honeycomb structure molding die according to its blueprint or specification.